WSL2-Linux-Kernel/arch/arm64/include/asm/pgtable-prot.h

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2016 ARM Ltd.
*/
#ifndef __ASM_PGTABLE_PROT_H
#define __ASM_PGTABLE_PROT_H
#include <asm/memory.h>
#include <asm/pgtable-hwdef.h>
#include <linux/const.h>
/*
* Software defined PTE bits definition.
*/
#define PTE_WRITE (PTE_DBM) /* same as DBM (51) */
#define PTE_DIRTY (_AT(pteval_t, 1) << 55)
#define PTE_SPECIAL (_AT(pteval_t, 1) << 56)
#define PTE_DEVMAP (_AT(pteval_t, 1) << 57)
#define PTE_PROT_NONE (_AT(pteval_t, 1) << 58) /* only when !PTE_VALID */
arm64/mm: Change THP helpers to comply with generic MM semantics pmd_present() and pmd_trans_huge() are expected to behave in the following manner during various phases of a given PMD. It is derived from a previous detailed discussion on this topic [1] and present THP documentation [2]. pmd_present(pmd): - Returns true if pmd refers to system RAM with a valid pmd_page(pmd) - Returns false if pmd refers to a migration or swap entry pmd_trans_huge(pmd): - Returns true if pmd refers to system RAM and is a trans huge mapping ------------------------------------------------------------------------- | PMD states | pmd_present | pmd_trans_huge | ------------------------------------------------------------------------- | Mapped | Yes | Yes | ------------------------------------------------------------------------- | Splitting | Yes | Yes | ------------------------------------------------------------------------- | Migration/Swap | No | No | ------------------------------------------------------------------------- The problem: PMD is first invalidated with pmdp_invalidate() before it's splitting. This invalidation clears PMD_SECT_VALID as below. PMD Split -> pmdp_invalidate() -> pmd_mkinvalid -> Clears PMD_SECT_VALID Once PMD_SECT_VALID gets cleared, it results in pmd_present() return false on the PMD entry. It will need another bit apart from PMD_SECT_VALID to re- affirm pmd_present() as true during the THP split process. To comply with above mentioned semantics, pmd_trans_huge() should also check pmd_present() first before testing presence of an actual transparent huge mapping. The solution: Ideally PMD_TYPE_SECT should have been used here instead. But it shares the bit position with PMD_SECT_VALID which is used for THP invalidation. Hence it will not be there for pmd_present() check after pmdp_invalidate(). A new software defined PMD_PRESENT_INVALID (bit 59) can be set on the PMD entry during invalidation which can help pmd_present() return true and in recognizing the fact that it still points to memory. This bit is transient. During the split process it will be overridden by a page table page representing normal pages in place of erstwhile huge page. Other pmdp_invalidate() callers always write a fresh PMD value on the entry overriding this transient PMD_PRESENT_INVALID bit, which makes it safe. [1]: https://lkml.org/lkml/2018/10/17/231 [2]: https://www.kernel.org/doc/Documentation/vm/transhuge.txt Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Suzuki Poulose <suzuki.poulose@arm.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Link: https://lore.kernel.org/r/1599627183-14453-2-git-send-email-anshuman.khandual@arm.com Signed-off-by: Will Deacon <will@kernel.org>
2020-09-09 07:53:02 +03:00
/*
* This bit indicates that the entry is present i.e. pmd_page()
* still points to a valid huge page in memory even if the pmd
* has been invalidated.
*/
#define PMD_PRESENT_INVALID (_AT(pteval_t, 1) << 59) /* only when !PMD_SECT_VALID */
#ifndef __ASSEMBLY__
#include <asm/cpufeature.h>
#include <asm/pgtable-types.h>
extern bool arm64_use_ng_mappings;
#define _PROT_DEFAULT (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
#define _PROT_SECT_DEFAULT (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
#define PTE_MAYBE_NG (arm64_use_ng_mappings ? PTE_NG : 0)
#define PMD_MAYBE_NG (arm64_use_ng_mappings ? PMD_SECT_NG : 0)
/*
* If we have userspace only BTI we don't want to mark kernel pages
* guarded even if the system does support BTI.
*/
#ifdef CONFIG_ARM64_BTI_KERNEL
#define PTE_MAYBE_GP (system_supports_bti() ? PTE_GP : 0)
#else
#define PTE_MAYBE_GP 0
#endif
#define PROT_DEFAULT (_PROT_DEFAULT | PTE_MAYBE_NG)
#define PROT_SECT_DEFAULT (_PROT_SECT_DEFAULT | PMD_MAYBE_NG)
#define PROT_DEVICE_nGnRnE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_DEVICE_nGnRnE))
#define PROT_DEVICE_nGnRE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_DEVICE_nGnRE))
#define PROT_NORMAL_NC (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_NC))
#define PROT_NORMAL (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL))
#define PROT_NORMAL_TAGGED (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_TAGGED))
#define PROT_SECT_DEVICE_nGnRE (PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_DEVICE_nGnRE))
#define PROT_SECT_NORMAL (PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_NORMAL))
#define PROT_SECT_NORMAL_EXEC (PROT_SECT_DEFAULT | PMD_SECT_UXN | PMD_ATTRINDX(MT_NORMAL))
#define _PAGE_DEFAULT (_PROT_DEFAULT | PTE_ATTRINDX(MT_NORMAL))
#define PAGE_KERNEL __pgprot(PROT_NORMAL)
#define PAGE_KERNEL_RO __pgprot((PROT_NORMAL & ~PTE_WRITE) | PTE_RDONLY)
#define PAGE_KERNEL_ROX __pgprot((PROT_NORMAL & ~(PTE_WRITE | PTE_PXN)) | PTE_RDONLY)
#define PAGE_KERNEL_EXEC __pgprot(PROT_NORMAL & ~PTE_PXN)
#define PAGE_KERNEL_EXEC_CONT __pgprot((PROT_NORMAL & ~PTE_PXN) | PTE_CONT)
#define PAGE_S2_MEMATTR(attr, has_fwb) \
({ \
u64 __val; \
if (has_fwb) \
__val = PTE_S2_MEMATTR(MT_S2_FWB_ ## attr); \
else \
__val = PTE_S2_MEMATTR(MT_S2_ ## attr); \
__val; \
})
#define PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_VALID) | PTE_PROT_NONE | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN)
/* shared+writable pages are clean by default, hence PTE_RDONLY|PTE_WRITE */
#define PAGE_SHARED __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)
#define PAGE_SHARED_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_WRITE)
#define PAGE_READONLY __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN)
#define PAGE_READONLY_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN)
#define PAGE_EXECONLY __pgprot(_PAGE_DEFAULT | PTE_RDONLY | PTE_NG | PTE_PXN)
#define __P000 PAGE_NONE
#define __P001 PAGE_READONLY
#define __P010 PAGE_READONLY
#define __P011 PAGE_READONLY
#define __P100 PAGE_READONLY_EXEC /* PAGE_EXECONLY if Enhanced PAN */
#define __P101 PAGE_READONLY_EXEC
#define __P110 PAGE_READONLY_EXEC
#define __P111 PAGE_READONLY_EXEC
#define __S000 PAGE_NONE
#define __S001 PAGE_READONLY
#define __S010 PAGE_SHARED
#define __S011 PAGE_SHARED
#define __S100 PAGE_READONLY_EXEC /* PAGE_EXECONLY if Enhanced PAN */
#define __S101 PAGE_READONLY_EXEC
#define __S110 PAGE_SHARED_EXEC
#define __S111 PAGE_SHARED_EXEC
#endif /* __ASSEMBLY__ */
#endif /* __ASM_PGTABLE_PROT_H */